Magnetic securing means for flexible printing plates



J. W. MARTT Nov. 16, 1965 MAGNETIC SECURING MEANS FOR FLEXIBLE PRINTING PLATES Filed Dec. 31, 1962 2 Sheets-Sheet 1 INVENTOR.

JUDSON W. MARTT A TTORNEYS'.

J- W. MARTT Nov. 16, 1965 MAGNETIC SECURING MEANS FOR FLEXIBLE PRINTING PLATES 2 Sheets-Sheet 2 Filed Dec. 31, 1962 INVENTOR. JUDSON W. MARTT ATTORNEY):

United States Patent 3,217,645 MAGNETIC SEEURING MEANS FUR FLEMBLE PRINTING PLATES Judson W. Martt, Weirton, W. Van, assigner to National Steel (Iorporation, a corporation of liieiaware Filed Dec. 31, 1%2, Ser. No. 2485612 6 Claims. (E Hill-415.1)

The present invention relates to printing apparatus, more particularly of the type in which a rotary cylinder is encompassed by a relatively thin, flexible ferrous impression or printing plate. The invention will be illustrated by way of example in connection with continuous strip lithography; but it is to be understood that it is applicable to other printing arts using thin, flexible ferrous metallic impression plates carried by impression cylinders.

In the art of continuous strip lithography, it is conventional to provide a continuously rotating impression cylinder that is encompassed by a thin flexible impression plate. The impression plate extends most of the way around the cylinder and is releasably secured along its end edges to the cylinder. To enable this securement of the impression plate, it is a common practice to recess the impression cylinder along its periphery parallel to its axis, and to bend the ends of the impression plate into the recess and secure them in the recess with the end edges of the impression plate disposed within the cylindrical contour of the impression cylinder. This arrangement is quite satisfactory for use in the printing of individual sheets, it being necessary only to make sure that the impression plate and not the gap between the secured ends of the impression plate registers with the sheet to be printed.

But with the advent of continuous strip printing, in which it is desired to make a repeating print on a continuous strip of material with no appreciable seam or space between the repeating print, the techniques of the prior art have been of litlte use, producing as they do a relatively wide gap between repeating prints.

Accordingly, it is an object of the present invention to provide printing apparatus for the rotary printing of continuous strip material, in which a repeating impression is produced that has virtually no gap between prints.

Another object of the present invention is the provision of printing apparatus which will be relatively simple and inexpensive to manufacture and assemble, easy to operate, maintain and repair, and rugged and durable in use.

Other objects and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompanying drawings, in which:

FIGURE 1 is an elevational view of an impression cylinder assembly according to the present invention;

FIGURE 2 is an enlarged fragmentary cross-sectional view taken on the line 2-2 of FIGURE 1;

FIGURE 3 is an enlarged fragmentary cross-sectional view taken on the line 33 of FIGURE 1, it being noteworthy that half of FIGURE 3 is disposed in one plane and the other half of FIGURE 3 is disposed in another plane, as indicated by the section line 33 of FIGURE 1;

FIGURE 4 is an enlarged fragmentary cross-sectional view taken on the line 4-4 of FIGURE 1;

FIGURE 5 is an enlarged fragmentary cross-sectional view taken on the line s s of FIGURE 1;

"ice

FIGURE 6 is a fragmentary view of one corner of an impression plate according to the present invention; and

FIGURE 7 is a view similar to FIGURE 4 but showing a modified form of the invention.

Referring now to the drawings in greater detail, there is shown an impression cylinder generally indicated at 1, for a rotary lithographic printing press. Cylinder 1 includes a central shaft 3 on which is journaled for rotation an assembly comprising bearer rings 5 one disposed at either end of a hollow cylinder body 7 having an accurately machined outer cylindrical periphery extending most of the length of cylinder 1.

A removable impression plate 9 is releasably secured to the outer periphery of cylinder body 7 in encompassing relationship. Impression plate 9 is of a length substantially equal to the peripheral extent of cylinder body 7. Plate 9 is thin and flexible and of ferrous metal. It may for example be stainless steel 0.011" thick. It is impression plate 9 that carries the inked impression to be trans ferred to the sheet or strip to be printed.

Means are provided for releasably clamping impres sion plate 9 to cylinder body 7, comprising a plate-clamping assembly I]; of which one is disposed at either end of cylinder body 7 in alignment with each other along a line parallel to the axis of the cylinder. Each assemly 11 includes a plate-clamping block 13 one of which is disposed in a recess in each opposite end of cylindeti' body 7 and releasably secured as by bolts to the cylinder. The structure of impression plate 9, in turn, coacts with the clamping assembly to secure plate 9 to body 7. That impression plate structure is best seen in FIGURE 6, it being understood that FIGURE 6 shows only one corner of the impression plate and that the other four corners are mirror images of each other along each edge of plate 9. Thus, each corner of plate 9 is provided with a tab 15 and with an ear 17 that has a pair of openings 19 therethrough. The margins of cylinder body 7, as best seen in FIGURE 3, are beveled as at 21 on the opposite sides of the clamping block recess, and tabs 15 are bent over those bevels and terminate within the cylindrical contour of cylinder body 7. Wedge blocks 23 are releasably secured in the recess by means of screws and bear against and secure the upper or outer surfaces of tabs 15 against the bevels at 21.

Plate adjustment blocks 25 are disposed within plateclamping blocks 13 for limited movement in a direction parallel to the axis of the cylinder, as is best seen in FIG- URE 2. Two bolts 27 extend between the side walls of clamping block 13 parallel to the axis of the cylinder, and a block 25 is mounted for sliding movement on each bolt 27. Each adjustment block 25 has a pair of upstanding legs, and an adjustment nut 29 is disposed between the legs of each block 25 and turns on a bolt 27. Rotation of nut 29 thus moves its associated block 25 in one direction or the other parallel to the axis of the cylinder.

Each ear 17 of impression plate 9 overlies one leg of an adjustment block 25 and is secured thereto by means of screws one passing through each opening 19. The recesses for the screws are countersunk so that the screw heads are flush with the periphery of the cylinder, as is best seen in FIGURES 2 and 3. Therefore, when ears 17 are secured to blocks 25 and adjustment nuts 29 are turned in a direction to make the blocks 25 move away from impression plate 9 at both ends of the cylinder, the adjacent ends of impression plate 9 will be drawn taut parallel to the axis of the cylinder.

It will therefore be seen that impression plate 9 has a pair of end edges 31 that are closely contiguous to each other and that are disposed parallel to the axis of the cylinder and that may be drawn taut by manipulation of blocks 25, and that lie both on the cylindrical contour of impression plate 9. Plate 9 also has a pair of circular side edges 33 that are held taut by the locking of tabs beneath wedge blocks 23. The side edges 33 of plate 9 are thus held firmly on the cylinder by means of wedge blocks 23, while the end edges 31 are held closely together to form a butt joint 35 by means of adjustment blocks 25.

An important part of the present invention is the provision of permanent magnets 37 that are elongated and that extend parallel to the axis of the cylinder closely subjacent butt joint 35 for the purpose of attracting and holding end edges 31 in abutting relationship. In the embodiment shown, there are four magnets 37 in length- Wise alignment with each other. Each magnet 37 is U- shaped in cross-section and has a pair of legs 39 that extend from an intermediate bight 41 radially outwardly toward but terminate short of end edges 31. One of legs 39 is thus disposed beneath each of the end portions of plate 9 adjacent end edges 31.

As is best seen in FIGURES 2 and 4, magnets 37 are disposed in a radially inwardly opening recess 43 that extends full length of cylinder body 7. Magnets 37 are inserted into recess 43 from below, that is, from the radially inner side. Recess 43 is of a depth substantially greater than the height of magnets 37, so that magnets 37 occupy the upper or radially outer end of the recess and leave a substantial portion of the height of the recess unoccupied by magnets 37. Instead, those lower or radially inner portions of the recess are occupied by wedge blocks 45 that carry rubber cushions 4-7 on their upper surfaces. Wedge blocks 45 are disposed between endwise adjacent magnets 37 and at the ends of magnets 37 adjacent the ends of cylinder body 7. A keeper bar 49 is welded to the radially inner side of cylinder body 7 and closes recess 43 and keeps magnets 37 and Wedge blocks 45 and cushions 47 all in assembly in recess 43. Cushions 47 thus perform the function of continuously urging magnets 37 against the top of recess 43 to prevent rattling of the magnets upon rapid rotation of the cylinder. A further keeper bar 51 closes the open ends of recess 43 to maintain the assembly of magnets 37 and wedge blocks 45 and cushions 47 in place against displacement in a direction parallel to the axis of the cylinder. In this connection, it should be noted that cushions 47 are under compression between magnets 37 and wedge blocks 45, not only radially of the cylinder but also parallel to the axis of the cylinder. Keeper bar 51 is screwed in place and can be readily removed for replacement or repair of the assemblies of magnets 37, wedge blocks 45 and cushions 4-7.

There is thus provided a construction in which not only are the corners of the impression plate anchored both in peripheral or hoop tension and also in tension parallel to the axis of the cylinder along the butted end edges 31, but also those butted end edges are drawn against and maintained in area contact with the cylindrical contour of the impression cylinder by means of strong permanent magnets beneath the surface of the impression cylinder. In this connection, it should be noted that the peripheral surface of the impression cylinder above the magnets is continuous, that is, there is no seam or joint in the impression cylinder beneath the butt joint 35. Thus, the cylindrical surface on which butt joint 35 rests may be machined with great accuracy and the joint may thus be so inconspicuous as to leave no visible trace on a strip during the continuous printing of the strip by the rotary printing press of the present invention.

A somewhat different embodiment of the invention is seen in FIGURE 7, which is a view in the same region as FIGURE 4. In FIGURE 7, in which parts corresponding to the parts in the previous embodiment are designated by the corresponding primed reference numerals, a recess 53 is provided in cylinder body 7' which opens radially outwardly instead of radially inwardly. Magnets 37 are disposed in recess 53 on top of rubber cushions 55; and a nonferrous metallic keeper bar 57 is recessed into cylinder body 7 and closes the top of recess 53 to keep magnets 37' forced snugly into recess 53 in compressive engagement with cusions 55 so as to prevent rattling of the magnets. The outer surface of keeper bar 57 is machined to the same curvature as the rest of cylinder body 7 so that the cylindrical periphery of cylinder body 7' is not interrupted by keeper bar 57. Screws pass through keeper bar 57 and into cylinder body 7' on either side of recess 53 thereby removably to retain keeper bar 57 on cylinder body 7'. As in the preceding embodiment, the cylindrical periphery of cylinder body 7 is thus continuous above magnets 37 so that the end edges of impression plate 9 along butt joint 35 are held firmly against keeper bar 57 in area contact with keeper bar 57.

One of the advantages of the embodiment of FIGURE 7 is that the nonferrous metallic nature of keeper bar 57 avoids short-circuiting magnets 37 across the ends of their legs 39'. The attraction of magnets 37 for the superposed end edge portions of impression plate 9' is thus stronger than if keeper bar 57 were of ferrous metal. An example of a suitable material for keeper bar 57 is brass.

From a consideration of the foregoing disclosure, therefore, it will be evident that all of the initially recited objects of the present invention have been achieved.

Although the present invention has been described and illustrated in connection with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Such modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

What is claimed is:

1. Apparatus for printing on strip material, comprising an impression cylinder, a thin flexible impression plate of magnetic ferrous metal encompassing the cylinder in cylindrical configuration and having its end edges parallel to the axis of the cylinder and being buttted together, the end edges of the impression plate being thin and flexible, the outer cylindrical contour of the impression cylinder underlying the end edges of the impression plate, magnet means within the contour of the impression cylinder adjacent and underlying both end edges of the impression plate thereby releasably to secure the end edges of the impression plate in area contact with the outer cylindrical surface of the impression cylinder, and means movable parallel to the length of the end edges of the impression plate to adjustably tension said end edges.

2. Printing apparatus as claimed in claim 1, the impression plate having corner portions adjacent the ends of the end edges of the impression plate, said corner portions extending within the cylindrical contour of the impression cylinder, and means on the outer side of said corner portions releasably clamping said corner portions to the impression cylinder.

3. Printing apparatus as claimed in claim 1, the magnet means comprising at least one elongated permanent magnet disposed parallel to the axis of the impression cylinder.

4. Printing apparatus as claimed in claim 3, the magnet means having a U-shaped cross section, one leg of the U being disposed beneath each end of the impression plate adjacent the end edges thereof.

5. Printing apparatus as claimed in claim I, the cylindrical surface of the impression cylinder being continuou beneath the end edges of the impression plate.

References Cited by the Examiner UNITED STATES PATENTS 12/1902 Such 101-375 11/1920 Novotny 101378 1,392,896 10/1921 Strawn 101-4151 1,939,681 12/1933 Fleming 1013S2 2,788,743 4/1957 Schwerin 101--3 82 FOREIGN PATENTS 186,648 8/ 1956 Austria. 596,749 10/ 1925 France.

EUGENE R. CAPOZIO, Primary Examiner.

ROBERT E. PULFREY, DAVID KLEIN, Examiners. 

1. APPARATUS FOR PRINTING ON STRIP MATERIAL, COMPRISING AN IMPRESSION CYLINDER, A THIN FLEXIBLE IMPRESSION PLATE OF MAGNETIC FERROUS METAWL ENCOMPASSING THE CYLINDER IN CYLINDRICAL CONFIGURATION AND HAVING ITS END EDGES PARALLEL TO THE AXIS OF THE CYLINDER AND BEING BUTTED TOGETHER, THE END EDGES OF THE IMPRESSION PLATE BEING THIN AND FLEXIBLE, THE OUTER CYLINDRICAL CONTOUR OF THE IMPRESSION CYLINDER UNDERLYING THE END EDGES OF THE IMPRESSION PLATE, MAGNET MEANS WITHIN THE CONTOUR OF THE IMPRESSION CYLINDER ADAJACENT AND UNDERLYING BOTH END EDGES OF THE IMPRESSION PLATE THEREBY RELEASABLY TO SECURE THE END EDGES OF THE IMPRESSION PLATE IN AREA CONTACT WITH THE OUTER CYLINDRICAL SURFACE OF THE IMPRESSION CYLINDER, AND MEAN MOVABLE PARALLEL TO THE LENGTH OF THE END EDGES OF THE IMPRESSION PLATE TO ADJUSTABLY TENSION SAID END EDGES. 